(1) Field of the Invention
The present invention relates to an image stabilizing circuit for a camcorder, and more particularly, to an image stabilizing circuit for a camcorder which stabilizes unstable images, which are produced by hand-trembling when a user is recording the images with the camcorder.
(2) Description of the Prior Art
Currently, camcorders and portable cameras having a video cassette recorder (VCR) are widely used as portable devices for recording moving pictures. However, when a user records the images with a camcorder, especially while the user is walking or in a moving vehicle, unstable and trembling images are recorded due to the user's hand-trembling. The trembling is a serious disadvantage when the user is recording the images with a high magnification ratio. Therefore, various image compensation circuits or devices have been developed to eliminate these disadvantages. For instance, an improved charge coupled device (CCD) or a buffer having large memory size is used for the compensation of the trembling images. For an example, a Japanese cooperation, SONY, developed a method to control a beam axis of the input beam with an active prism. Hereinafter, conventional image stabilizing circuits and devices will be described in detail with reference to the attached drawings.
FIG. 1 illustrates the conventional method of stabilizing the recorded unstable image by using a buffer having a large memory size, in which the input image is temporarily stored. In this method, the system reproduces the input image from the buffer, in a normal mode, without any modification. However, in a compensating mode, the system shifts a frame of the image stored in the buffer according to the hand trembling motion, and the system selects the shifted frame from the stored image in the buffer, and the system finally magnifies and reproduces the selected frame.
The above-described method is disadvantageous in that degradation of the resolution occurs due to the magnification process, and this method requires a buffer having a large memory capacity.
FIG. 2 illustrates the conventional method of stabilizing the recorded image by using a large or high density charge coupled device(CCD). This method shifts an image frame on the CCD according to the hand-trembling. and selects the shifted image frame on the CCD, and reproduces the selected image. This method should use a large CCD or a CCD having high density so that the user can record the full image on the CCD without any loss of the image, in spite of the hand-trembling motion. As described above, the motions of images resulting from user hand-trembling is compensated by shifting the image frame on a buffer or a CCD according to the hand-trembling.
FIG. 3 illustrates the conventional method of stabilizing the recorded image by using a variable angle prism (also called as an active prism). This method controls the beam axis of the input beam with the active prism according to the hand trembling. The advantages of this method include fine resolution and wide compensation range. This is due to the fact that the method controls the beam axis mechanically, and does not have to magnify the selected image. However, this method has a certain disadvantage because the active prism is mechanically controlled. That is, if the user records the image with high magnification ratio or if the camcorder is moving or trembling with high speed when recording images, the resolution of the image will be greatly reduced since the active prism cannot change the beam axis of the input image mechanically according to the fast movement of the camcorder. Furthermore, the device is mechanically complex and expensive.